Almeida made his professional mixed martial arts debut in September 2011. He fought extensively in his native Brazil and amassed a record of 8–0 with four wins via KO before making his Legacy FC debut.[6]

Almeida made his Legacy Fighting Championship debut against Cody Williams on November 16, 2012 at Legacy FC 15. Almeida won the fight via KO in the first round.[7]

Almeida faced George Pacurariu on December 6, 2013 at Legacy FC 26.[8] Almeida won the fight via TKO in the first round.[9]

Almeida was expected to face Aaron Philips on June 20, 2014 at Legacy FC 32 for the vacant Legacy FC Bantamweight Championship. However, Philips pulled out of the fight and was replaced by Caio Machado.[10] Almeida won the fight via TKO in the first round to win the Legacy FC Bantamweight Championship.[11]

In June 2014, the UFC announced that they had signed Almeida to a multi-fight contract.[12]

Almeida made his promotional debut against Tim Gorman on November 8, 2014 at UFC Fight Night 56.[13] Almeida won the fight via unanimous decision, marking the first time ever he didn't finish an opponent in his pro career.[14] The fight also earned Almeida his first Fight of the Night bonus award.[15]

Almeida faced Yves Jabouin on April 25, 2015 at UFC 186.[16] He won the fight via TKO in the first round.[17] This win also secured Almedia his first Performance of the Night bonus award.[18]

Almeida faced Brad Pickett on July 11, 2015 at UFC 189.[19] Despite getting dropped twice in the first round, Almeida won the fight via knockout with a flying knee in the second round and also earned a Performance of the Night bonus.[20][21]

Almeida faced fellow undefeated prospect Cody Garbrandt on May 29, 2016 at UFC Fight Night 88.[25] Despite being the betting favorite, Almeida had no answer for Garbrandt's hand speed and accuracy and lost the fight via knockout in the first round.[26]